MutableNetwork<Integer, String> undirectedNetwork =
        NetworkBuilder.undirected().allowsParallelEdges(true).allowsSelfLoops(true).build();
    undirectedNetwork.addNode(N0);
    undirectedNetwork.addEdge(N1, N2, E12);
    undirectedNetwork.addEdge(N2, N1, E12_A); // adds parallel edge, won't be in Graph edges
    undirectedNetwork.addEdge(N1, N3, E13);
    undirectedNetwork.addEdge(N4, N4, E44);
    containsExactlySanityCheck(

  private static final int NODE_POOL_SIZE = 1000; // must be >> NUM_NODES

  @Test
  public void directedNetwork() {
    testNetworkMutation(NetworkBuilder.directed());
  }

  @Test
  public void undirectedNetwork() {
    testNetworkMutation(NetworkBuilder.undirected());
  }

  private static void testNetworkMutation(NetworkBuilder<? super Integer, Object> networkBuilder) {